Got in my wideband

[96talontso]

At idle im running at about 17.0 and when im on it hard it runs rich at 11.1 and its pretty steady there. Im 14 psi with stock turbo and all stock fuel parts. I am getting a couple stutters here and there though and i have no vacuum leak. Why am i runnin so lean at idle and so rich when im on it hard?

 

[jooc]

14.1 is pretty much perfect air/fuel.. 17 at idle . now is it bouncing from like 14 to 17 or just stays at 17 and .. when you stomp on the gas.. it does seem to sound right that your at 11 considering your untuned and all stock?

 

[WES_393]

You want 14.7 at idle. Your actually not running very rich at WOT, most tune for 11.1-11.5 at WOT on pump gas. That's typically about all you can get away with depending on the setup. So your WOT is good, but 17 at idle makes me think you have an exhaust leak that's drawing in air.

 

[mattasi]

Mine is around 11.5 at WOT, it's the idle I would be worried about.

If he has an exhaust leak, then wouldn't that throw the 11@WOT out of wack also?

 

[Latch]

Best idle / cruise is around 14,7

Are you running the stock front O2 ?

 

[2g_turtle]

Yeah around 14 is good, my idle was around 16, 17 and I had an exhaust leak at my manifold, fixed it and it help the lean problem

 

[96talontso]

Yup im on the stock front o2 sensor, car hasnt been running for a while now though since im installing fmic fuel pump afpr and e3b16g

 

[jtmcinder]

14.1 is pretty much perfect air/fuel..

I'd love to hear the explanation for this assertion. (Or maybe I just need to learn a new definition for "perfect.")

As to exhaust leaks, do these really draw in air? (For once that's not rhetorical.) Of course an exhaust leak will bleed air at WOT; I'm asking if they really switch to letting in air at idle.

 

[96ETT]

Yes, in between exhaust pulses they can suck air in. This would be more of a concern after the turbine or at no boost because of the lower pressure in the exhaust stream.

 

[rEclipserGST]

Which wideband is this? Did you calibrate it?

What does it read while cruising steady?

 

[marcman804]

I recently found a pretty nasty exahust leak in my exhaust by the muffler and my readings are still 14.5 - 14.7 at idle and 11.3 - 11.5 at WOT. I think you may have a calibration issue with your wideband. By the way, which wideband are you running with?

 

[Arthris]

11 at wot is conserning. I think its suppose to be around 9:1 is it not? Atleast on the 1gs it is. Swor ive read that the 2gs are almost the same. Would be nice ro know whar ## short term fuel trim is. Im sure its maxed out. Have you tried disconecting the battery overnight. That will reset the ecu. OBDII ecus take a while to fully reset.

 

[jtmcinder]

Yes, in between exhaust pulses they can suck air in. This would be more of a concern after the turbine or an no boost because of the lower pressure in the exhaust stream.

Woo hoo! I learned something today. Thanks.

 

[Miakehl]

Wouldn't an exhaust leak only make a difference if it's within earshot of the o2? I don't see how a downstream leak could affect AFRs. Say if you had a dumped downpipe or side exit setup...

 

[96ETT]

14.1 is pretty much perfect air/fuel..

Is this some sort of averaged value for our "gasoline" that is really E10? Im also wondering where this came from...

Wouldn't an exhaust leak only make a difference if it's within earshot of the o2? I don't see how a downstream leak could affect AFRs. Say if you had a dumped downpipe or side exit setup...

Well you are talking about different things. The other post up there mentioned fixing a leak in the manifold and that helping. The manifold is certainly up stream of either O2 so air that got sucked in at the manifold will have an effect on the O2 readings.

A downstream leak would not matter to the O2. The only way this could matter is if your O2 sensor is near the exhaust exit as again, between cylinder pulses air can travel in the pipe.

 

[WES_393]

If he has an exhaust leak, then wouldn't that throw the 11@WOT out of wack also?

Not necessarily, the wideband just reads the ratio of air to fuel, not the amount of each. So by losing some gasses your not messing with the ratio, just the amount of gas that makes it out of the exhaust pipe. Just like using an open dump, it doesn't mess with O2 readings because the exhaust gasses that are dumped have the same A/F ratio as those that hit the O2 sensor.

The idea behind exhaust leaks throwing off O2 sensors is that exhaust pulses will draw in fresh air. The air will cause the A/F ratio to look more lean to the wideband than it actually is. Since exhaust only pulses at low engine speed, it would only throw off the A/F ratio at idle. WOT and cruise would look perfect.

 

[96talontso]

Innovate mtx-l and yes i calibrated it.

 

[96ETT]

Not necessarily, the wideband just reads the ratio of air to fuel, not the amount of each. So by losing some gasses your not messing with the ratio, just the amount of gas that makes it out of the exhaust pipe. Just like using an open dump, it doesn't mess with O2 readings because the exhaust gasses that are dumped have the same A/F ratio as those that hit the O2 sensor.

True.

The idea behind exhaust leaks throwing off O2 sensors is that exhaust pulses will draw in fresh air. The air will cause the A/F ratio to look more lean to the wideband than it actually is. Since exhaust only pulses at low engine speed, it would only throw off the A/F ratio at idle. WOT and cruise would look perfect.

Not true. The exhaust always pulses, no matter what the speed. There are only four cylinders firing within 720 degrees of rotation. So every 180 degrees there is a firing even with a pressure spike. Until the next firing event the pressure decays to some lower value. Most gauges would read the pressure as some average of the peak and trough of the pressure wave, usually closer to the lowest value though. The main reason it doesn't affect AFR much at higher LOADS is that the pressure is greater in the exhaust mainly before the turbine. This means that even though the exhaust is pulsing, the lowest pressure in that pulse is still well above ambient and therefore no fresh air is pulled in. It is when the lower value in the pressure wave is near ambient that air is sucked in.

 

[rEclipserGST]

I had an exhaust leak INBETWEEN the o2 housing & my wideband. The wideband's afr was affecting. But then again, most of the flex pipe was destroyed

No issues now. Especially since the exhaust leaks are fixed & it is calibrated.